GB2284430A

GB2284430A - Self-lubricating hard material

Info

Publication number: GB2284430A
Application number: GB9322300A
Authority: GB
Inventors: Kei Tokumoto; Akira Tanaka; Osamu Ishimashi
Original assignee: Nippon Tungsten Co Ltd
Current assignee: Nippon Tungsten Co Ltd
Priority date: 1993-10-29
Filing date: 1993-10-29
Publication date: 1995-06-07
Also published as: NL9400405A; GB9322300D0

Abstract

A self-lubricating hard material suitable for shaft bearings and sealing rings is provided in which at least one self-lubricating material comprising BN or a sulfide of Cr, Mn or a transition metal from columns IVa to VIa in the periodic table or a solid solution or double sulfide of these sulfides which may contain graphite is dispersed in an amount of 0.1 - 50 vol% in a hard material.

Description

SELF-LUBRICATING HARD MATERIAL FIELD OF TECHNOLOGY The present material is one that relates to self-lubricating hard material suitable for cienients that slide such as sealings and bearings, and is particularly suitable for use under high loads.

BACKGROUND OF 1HE 1ECI INOLOGY In prior mechanical seals, the sliding surfaces that sealed fluids by contacting and sliding against companion materials appropriately had flat surfaces, and there were no bores present in these surfaces (or at least they were not present intentionally).

There are various coiiibinations of these types of mechanical seals, in applications with large PV values (P is the sealed fluid pressure and V is the peripheral velocity) they are used in combinations of hard metal/carbon and hard metal/hard metal. On the other hand, there has been a recent demand for high performance pumps and PV values have also increased. With the prior hard metal/carbon, the latter deforms and leaks fluid because of the high heat, and with the hard metal/hard metal there are heat cracks on the sliding surface leading to leakage or seal rupture problems.

The response to these problems was to change the shape of the seal. For example, there are end surface lubrication seals (hydrostatic seals) where holes are furnished that pass through the sliding surface and the other surface and a pump sends in lubrication fluid from the holes in the other surface, and there are such as the thermohydrodynamic seals and hydrodynamic seals where channels or notchcs are furnished in the sliding surface from the fluid side nearly to the center, and the sealing fluid which plays the lubrication role during operation is led to the sliding portion by a wedge effect based on the viscosity of the fluid. These can be used at higher PV values than prior seais because they reduce the coefficient of friction.

However, in order for such hydrostatic seals, hydrodynamic seals and thermohydrodynamic seals to offer these effects the hard metal must undergo complicated processing, which makes the processing time markedly longer than with prior seals because of the hard metal is so difficult to process. Further, when hard metal has a complicated shape the pressure concentration tends to weaken and it tend to collapse.

Consequently these types of seal can only be used in limited applications at present, and there is a demand for new materials that do not require such processing.

In order to resolve this problem, hard materials with dispersed bores were developed as in Japanese Patent Disclosure Hei 1-283479 and in United States Patent 4925490.

Althbugh this bore dispersed material is superior in an environment containing fluid that plays a lubricating role such as oil, the bores have no effect in an environment where such fluid is not present, so that the performance is no more than when there are no bores at all. That is, in cases when the sliding occurs under dry type high loads shortly after the start of operation (on the order of a few minutes) as with the bearings of vertical shaft sluped flow pumps, sliding cracks tend to occur, and bore dispersed materials are unsuitable for resolving problems such as these.

Because of this a hard metal in which sliding cracks tend not to occur was proposed as seen in Japanese Patent Disclosure Sho 63-69938. But there are cases of cracks occurring when these types of hard metal are used under severe conditions such as under high loads and/or high rotation speeds, leading to rupture in extreme cases.

It is believed that applications of self-lubricating materials are desirable for resolving the problems above. We may classify self-lubricating materials into self-lubricating materials that are included in base soft materials (alloys) and self-lubricating materials included in base hard materials. The former cannot be used under high load conditions such as under sliding at high speeds or when the surface pressure is high.

The latter are ones where bores are included in the hard material and self-lubricating materials are introduced into these bores by an impregnation method (Japanese Patent Disclosure Sho 61-281073, Japanese Patent Disclosure Hei 1108167, and Japanese Patent Disclosure Hei 1-176010). With these materials the solid scif-iubricating substances tend to localize in the vicinity of the material surface, and the selflubricating effect does not continue for long time periods because they tend to peel off. Furthermore there is a need to enlarge the bores to a certain degree in order to introduce the solid lubricating materials, and there have been problems such as their essentially low strength.

The present invention is one whose object lies in offering a self-lubricating hard material that can be used at high PV values, whose shape can be simplified and that is easy to process, and that is suited for sliding materials such as long-life bearings and seal ring bearings and without the defect of tending to rupture because of complicated shapes.

As will be apparent from the prior technology discussed above, the said objects cannot be attained by a method that introduces self-lubricating substances following the impregnation method. It is clear that a suitable method will be a conventional powder metallurgy method, that is a method in which the required substances and elements are all mixed before sintering.

The preferred self-lubricating substances are such as graphite, WS2, MoS2 and BN, whose coefficients of friction are respectively 0.3, 0.28, 0.25 and 0.2 (Matsunaga and Tsutani, Kotai Junkatsu HANDOBUKKU [Solid Lubricant Handbook]), Koshobo, (1978), 540.4). however, decomposition and the like occur under sintering because they have little heat stability in vacuum, and it is considercd useless to include them in hard materials whose sintering temperatures are comparatively high.

As a result of keen investigations to overcome this, we discovered that MoS2 and WS2 decompose and cannot be sintered (cannot be residual after sintering), and it is only BN that does not decompose and that is still residual after sintering.

After further investigations into sulfides, we discovered that sulfides of Cr, Mn and transition metals in the IVa to VIa columns in the periodic table show little decomposition under sintering and are residual after sintering. Further, we also discovered that the coefficient of friction of materials containing both of these declined after the additions were made.

On the other hand and from another viewpoint, when we prepared materials with additions of hard materials that differed from the main ingredients in the hard materials to which they were added, we discovered that their coefficients of friction dropped below the coefficients of friction before the additions, we discovered that there is a kind of self-lubricating action.

The present invention therefore provides the following: (A) Self-lubricating hard material characterized in that: one or more types of self-lubricating materials comprising BN, or sulfides of Cr, Mn and transition metals in columns IVa to Va of the periodic table, or solid solutions or double sulfides of these sulfides are dispersed in proportions of 0.1 to 50 vol% in hard material comprising a matrix.

(B) Self-lubricating hard material characterized in that: one or more types of self-lubricating materials comprising BN, or sulfides of Cr, Mn and transition metals in columns IVa to Va of the periodic table, or solid solutions or double sulfides of these sulfides and carbon that is preferably graphite are dispersed in proportions of 0.1 to 50 vol% in hard material comprising a matrix.

(C) Self-lubricating hard material described in (A) or (B) characterized in that the hard material matrix is 50 to 99.9 wt% WC and the remainder is a hard metal comprising one or more types in the iron family of metals.

(D) Self-lubricating hard material described in (A) or (B) characterized in that the hard material matrix comprises one or more types of hard materials comprising carbides, nitrides and borides of transition metals in columns IVa to VIa in the periodic table and two or more types of. these in solid solution or as compounds.

(E) Self-lubricating hard material described in (A) or (B) characterized in that the hard material matrix comprises one or more types of hard materials comprising carbides, nitrides and borides of transition metals in columns IVa to VIa in the periodic table and two or more types of these in solid solution or as compounds is 50 to 99.9 wt% and the remainder comprises one or more iron family metal.

(F) Self-lubricating hard material described in (A) or (B) characterized in that the hard material matrix comprises one or more types of hard materials comprising carbides, nitrides and borides of transition metals in columns IVa to VIa in the periodic table and two or more types of these in solid solution or as compounds is 50 to 99.9 wt% and the remainder comprises one or more iron family metal, and a portion or all of the hard material is a compound with a portion of iron family metal and/or one or more types of added self-lubricating material.

(G) Self-lubricating hard material described in (A) or (B) characterized in that the hard material matrix is a ceramic comprising one or more types of hard materials comprising SiC, Si3N4, A1203, AlN, MgO, Zero2, CaO, Y203 and carbides, nitrides and borides of transition metals in columns IVa to VIa of the periodic table and solid solutions or compounds of two or more types of these.

(H) Self-lubricating hard material characterized in that there is a first hard material that is either one or more types of hard materials comprising carbides, nitrides and carbides of transition metals in columns IVa to VIa of the periodic table and solid solutions or compounds of two types or more of these, or it is one where one or more types of the said hard material is 50 to 99.9 wt% and the remainder comprises one or more types of iron family metals, there is a second hard material comprising one or more types of hard materials comprising SiC, Si3N4, A1203, AIN, MgO, Zero2, CaO, Y203 and oxides of rare earth elements and solid solutions or compounds of two types or more of these, and the first hard material is substituted in the second hard material in a proportion of 0.1 to 80 vol%.

(I) Self-lubricating hard material described in (H) characterized in that one or more types of self lubricating hard materials comprising BN or carbon that is preferably graphite or sulfides of Cr, Mn and transition metals in columns IVa to Va in the periodic table or solid solutions or double sulfides of these sulfides are dispersed in the hard material matrix in a proportion of 0.1 to 50 vol%.

The reasons for the limitations will be given next. The reason for the one or more types of self-lubricating materials comprising BN or sulfides of Cr, Mn and transition metals of columns IVa to Va in the periodic table or solid solutions or double sulfides of these sulfides being 0.1 to 50 vol% is because below 0.1 vol% there is no self-lubricating effect and because the strength decreases at over 50 vol%.

The reasons for the one or more types of self-lubricating hard materials comprising BN or sulfides and the carbon that is preferably graphite being 0.1 to 50 vol% are the same reasons as above. The reason for not having it contain graphite alone is because this would cause sliding performance to deteriorate.

The reasons why the WC or one or more types of hard materials (carbides, nitrides and borides of transition metals in columns IVa to VIa of the periodic table and solid solutions or corripounds of two or more of these) are 50 to 99.9 wt% and the residue is a hard material that is one or more types of iron family metals are because below 50 wt% there is too little hardness in the hard material portion and the material softens, while at over 99.9 wt% the amount of bound metal is insufficient and it sinters poorly.Another reason for imposing this limitation is that wheel tiie hard material portion that is the matrix is all of the hard materials described above, the sintering temperature becomes high, it becomes possible to sinter under such as hot pressing, and such materials are well suitable for applications requiring wear resistance and corrosion resistance.

Another reason for this limitation is that the so called ceramic described in (G) can be used as material in which selflubricating materials are dispersed by sintering under ordinary pressure or by hot pressing, and such materials are particularly well suitable for applications requiring wear resistance and corrosion resistance.

The combination of hard materials described in (H) will be discussed next. The reason for the first hard material being a hard metal system (that is, one that comprises either one or more types of hard materials comprising carbides, nitrides or borides of transition metals in columns IVa to VIa of the periodic table and solid solutions of two or more of these or one where one or more types of the said hard materials are 50 to 99.9 wt% and the remainder is one or more types of iron family metals) being given addition of a second hard material ceramic (that is, one or more types of hard materials comprising SiC, Si3N4, A1203, AIN, MgO, Zero2, CaO, Y203 and oxides of rare earth elements and solid solutions or compounds of two types or more of these) in a substitution addition at 0.1 to 80 vol% is because we discovered that such combinations have the effect of lowering the coefficient oi friction. Although the reason for this lowering effect is not clear, we do know from experience that sliding different types of materials together is said to decrease the amount of friction compared to sliding identical materials together, and the reason is thought to have some connection with this.Further, the reason for the ceramic being 0.1 to 80 vol% is that below 0.1 vol% there is no effect of lowering the coefficient of friction, and at over 80 vol% the effect of the dispersed ceramic itself is greater than the combined effect, so that as a result there comes to be no effect of lowering the coefficient of friction.

Further, the limitation of using the hard metal/ceramic complex material as the hard material is that a still greater effect is displayed when self-lubricating materials such as BN or sulfides or carbon that is preferably graphite are dispersed.

PREFERRED MODE FOR WORKING THE INVENTION The following Examples are given by way of illustration only in order to explain the present invention in further detail.

EXAMPLE 1 Various types of powders having average particle diameters of 1 to 6 llm were used as the starting powders, they were blended according to the matrix material blend compositions in Table 1, and were mixed in a ball mill for three days by wet method mixing in methanol. After drying the mixed powder, paraffin dissolved in trichloroethane was added at 2 wt% of the powder, and then was mixed and dried to obtain the mother powder for the matrix material.

This mother powder was given addition of BN powder (2 m particle diameter) in the amounts shown in Table 1 and then mixed in a mixer to obtain the starting powders for each sample.

These powders were press formed as tablets of 5.5 x 10 x 30 mm under pressure of I ton/cm2, and were presintered by heating for 10 hours up to 800"C in a vacuum (about 0.1 torr).

Then they were sintered for one hour at the respective temperatures shown in Table 1 under a vacuum of 0.6 to 0.8 torr to obtain materials 1 to 21 of the present invention and comparative materials 1 to 3. Materials 20 and 21 of the present invention could not be sintered by conventional vacuum sintering, so they were hot pressed under conditions of 1,7000C and 100 kg/cm2.

In Table 1 the WC/TiCfraC with a single star indicates a solid solution of 50 wt% WC-30 wt% TIC-20 wt% TaC, and the TiC/TiN with double stars indicates a solid solution of 50 wt% TiC-50 wt% TiN.

The materials 1 to 21 of the present invention and.

comparative materials 1 to 3 that were thus obtained were first ground with a diamond wheel to make four 4 x 8 x 24 mm JIS deflection test pieces for each. These test pieces were measured for hardness (HRA), and their deflection strength was measured by 3-point bending at span intervals of 20 mm.

The results are as shown in Table 1. The hardness of the materials of the present invention was over 65 HRA and the deflective strength was over 50 kg/mm2. On the other hand comparative material 2 had too much BN and was unsintered, and was so small it could not even be measured. The hardness of comparative example 3 was too little to make it of practical use. That is, only the materials of the present invention and comparative example 1 could be offered for practical use in terms of hardness and deflection.

Next, upon inspecting the textures of the materials shown in Table 1, BN was found as gray color in samples 1 to 21 of the present invention but naturally could not be found in comparative example 1. Upon X-ray diffraction, materials 1 to 21 of the present invention showed diffraction lines of (0, 0, 2) planes in hexagonal BN where d = 3.33 A, while there were naturally none found with comparative material 1. That is, it was found that the added BN definitely resided in materials I to 21 of the present invention.

Further, portions of the materials also had borides and double borides comprising Co and W present so that the BN portions reacted with the matrix metal ingredients to form borides, and this is no problem.

EXAMPLE 2 Various types of powders having average particle diameters of 1 to 5 llm were used as the starting powders, they were blended according to the matrix material blend compositions in Table 2, and were mixed in a ball mill for three days by wet method mixing in methanol. After drying the mixed powder, paraffin dissolved in trichloroethane was added at 2 wt% of the powder, and then was mixed and dried to obtain the mother powder for the matrix alloy.

This mother powder was given addition of selflubricating materials of the types and in the amounts shown in Table 2 and then mixed in a mixer to obtain the starting powders for each sample.

These powders were press formed as tablets of 5.5 x 10 x 30 mm under pressure of 1 tonicm2 and were presintered by heating for 10 hours up to 8000C in a vacuum (about 0.1 torr).

Then they were sintered for one hour at the respective temperatures shown in Table 1 under a vacuum of 0.6 to 0.8 torr to obtain materials 22 to 29 of the present invention and comparative materials 4 to 7. Materials 28 and 29 of the present invention could not be sintered by conventional vacuum sintering, so the former was hot pressed under conditions of 1,900"C and 100 kg/cm2, and the latter was atmospherically sintered at 1 ,6000C in N2 gas at 1 atmospheric pressure.

The materials 22 to 29 of the present invention and comparative materials 4 to 7 that were thus obtained were first ground with a diamond wheel to make four 4 x 8 x 24 mm JIS deflection test pieces for each. These test pieces were measured for hardness (HRA), and their deflective strength was measured by 3-point bending at span intervals of 20 mm.

The results are as shown in Table 2. The hardness of materials 22 to 29 of the present invention was over 65 HRA and the deflective strength was over 50 kg/mm2 (except materials 28 and 29 of the present invention), making it clear that they could be offered for practical use. Materials 28 and 29 of the present invention had low deflection strengths of 38 and 47 kg/mm2, but this was because the base ceramic had lower strength than the hard alloys as shown for comparative materials 6 and 7. However, they could be offered for applications under conditions of comparatively high speeds and low loads.

Next, upon inspecting the textures of the materials shown in Table 2, with materials 22 to 29 of the present invention the added BN, Ti S2, Task, MnS and graphite were all residual. On the other hand they were ilot found in comparative material 5 to which MoS2 had been added. That is, in the case of sulfides only stable sulfides such as TiS2 TaS2 and MnS were found to be residual.

EXAMPLE 3 Various types of powders having average particle diameters of 1 to 5 um were used as the starting powders, they were blended as shown in Table 3, WC and Co were used as the first hard materials and the second hard materials SiC, AIN, Awl203, MgO and Y203 were respectively blended therein as substituents, and they were mixed in a ball mill for three days by wet method mixing in methanol. After drying the mixed powder, paraffin dissolved in trichloroethane was added at 2 wt% of the powder, and then was mixed and dried to obtain the mixed powder.

Then self-lubricating materials were added to these mixed powders in the amounts and types shown in Table 3 which were then mixed in a mixer to obtain ihe mixed powders for each sample.

These powders were press formed as tablets of 5.5 x 10 x 30 mm under pressure of 1 ton/cm2, and were presintered by heating for 10 hours up to 8000C in a vacuum (about 0.1 torr).

Then they were sintered for one hour at the respective temperatures shown in Table 3 under a vacuum of 0.6 to 0.8 torr to obtain materials 30 to 40 of the present invention and comparative material 8.

The materials 30 to 40 of the present invention and comparative material 8 that were thus obtained were first ground with a diamond wheel to make four 4 x 8 x 24 mm JIS deflection test pieces for each. These test pieces were measured for hardness (HRA), and their deflective strength was measured by 3-point bending at span intervals of 20 mm.

The results are as shown in Table 3. The hardness of materials 30 to 40 of the present invention was over 65 HRA and the deflective strength was over 50 kg/mm2, making it clear that they could be offered for practical use.

EXAMPLE 4 Examples 1, 2 and 3 showed how the materials of the present invention are obtained. Here the coefficients of friction of various of these materials are measured.

Ring test pieces having sliding dimensions of 20 mm interior diameter, 34 mm outer diameter and 5 mm thickness were prepared by methods based on Examples 1, 2 and 3.

These sliding surfaces were lapped to on the order of 0.2 S, and were given degreasing treatment by ultrasonic wave washing.

WC-10% Co with sliding surfaces of 0.2 x 3 mm2 on these rings were slid while pressed by a 3.0 kg load W (surface pressure 500 kg/cm2) and frictional force F was measured. The number of rotations was successively varied at 600, 1,000, 2,000 and 3,000 rpm, and these were maintained for 2 minutes, 2 minutes, 14 minutes and 14 minutes. Then the coefficient of friction was obtained by F/W, and assessments were done by their average values u The R measured by the above method are shown in Tables 1 through 3. While comparative example 1 had R = 0.56 in Table 1, the R of 1,2,3,5, 9, 13, 14, 15, 16, 17 and 20 of the present invention were 0.39 to 0.47, clearly showing that the coefficients of friction were smaller by 16 to 30%. That is, it can be said that sliding performance improved by 16 to 30%.

The u of materials 22, 24 and 26 of the present invention where the matrix materials were hard alloys as shown in Table 2 were 0.43 to 0.45, which shows a coefficient of friction 20 to 23% smaller than the u = 0.56 of comparative material 1. When the matrix material was ceramic as in materials 28 and 29 of the present invention the u was 0.47 and 0.43, showing a 22% and 26% smaller coefficient of friction compared to the u = 0.60 and 0.58 of comparative examples 6 and 7. That is, in all instances the sliding performance is improved 20 to 26%.

Further, comparative material 4 has hard alloy for its matrix material and the self-lubricating material is all graphite but its u is 0.50, it is superior to the u = 0.56 of comparative material 1 (hard alloy) but is inferior to 1, 2, 3 and 26 of the present invention. Accordingly it was placed outside the range of the limitations.

In Table 3, the materials 30, 31, 32, 33 and 34 of the present invention where ceramics were added as the second hard material to the first hard material (hard alloy) had .. of 0.42 to 0.49, showing a 13 to 25% smaller coefficient of friction than the u = 0.56 of comparative material 1. Here comparative material 8 was also a combination of a first hard material and a second hard material, but iii this case the u was a large 0.55 and so was excluded from the range of the limitations.Further, materials 37, 38, 39 and 40 of the present invention where combinations of a first hard material and a second hard material were taken as the matrix material and self-lubricating materials were added thereto had u of 0.39 to 0.44, showing a coefficient of friction 21 to 30% smaller than the 11 = 0.56 of comparative material 1.

The coefficients of friction of the materials of the present invention are smaller than those of the comparative materials as shown above, and accordingly it may be said that their sliding performances are superior.

EXAMPLE 5 Finally we evaluated performance when used as seal rings. Test rings having sliding dimensions of 41 mm inner diameter and 56 mm outer diameter were prepared by the methods in Examples 1 and 2, and their sliding surfaces were lap finished. Then graphite rings with sliding surface dimensions of 43 mm inner diameter and 52 mm outer diameter were prepared as the companion materials, and their sliding surfaces were also lap finished. These were attached to a conventional mechanical seal test apparatus. The running conditions for the mechanical seals were as follows. That is, they were tap water as the sealing fluid, a sealing fluid pressure of 15 kg/cm2 and a revolution of 410 rpm. Then the average power required up to 1 hour after start of running was obtained.Since a large average required power indicates a large coefficient of friction, the sliding performance was evaluated by the size of the average required power for sake of convenience.

Following this method, the average required power was first measured for material 2, 13 and 20 of the present invention and comparative material 1 shown in Table 1. Then the average required power was measured for material 27 of the present invention and comparative material 4 shown in Table 2. Taking the required power for comparative material 1 as 1 and speaking in terms of power ratios based on that, materials 2, 13, 20 and 27 of the present invention showed 0.5, 0.5, 0.55 and 0.6, while comparative example 4 was 0.7. That is, the self-lubricating materials of the present invention may be said to have performance that is superior to prior hard alloys and prior materials where graphite was added to hard alloys.

POSSIBILITY OF INDUSTRIAL UTILIZATION As described above, the self-lubricating hard materials of the present invention have small coefficients of friction and increased sliding performance, without much lowering of the high hardness that is the strong point of the hard alloys or ceramics of prior hard materials or much lowering of the high deflective strength that is the strong point of the former. Consequently it is well suited for various types of materials used as sliding materials, particularly those used under conditions of high loads such as shaft bearings and seal rings.

The present invention has been described above purely by way of example, and modifications may be made within the invention.

Table 1

e f g h i a vc TIC TIC NbC Cr Cr1C2 No No2C * TIN ** @@ Fe Co TI (Ha@) (@@/@@) (@@) 1 93.5 6.3 5 1360 81 3 120 0 47 2 93.5 65 15 1360 74 1 82 0.39 3 93.5 65 30 1360 65.3 70 0 43 4 78.2 1.@ 20 15 1320 65.2 92 5 74.9 51 20 15 1320 65.@ 88 0 40 6 77 5 25 20 15 1320 65.9 87 7 76.6 33 20 15 1320 66.2 90 8 91.5 35 5.0 15 1400 74 2 78 9 91.5 3.5 0.1 0.2 50 15 1430 74 3 75 0 40 10 91.0 9.0 15 1340 71 0 84 11 87.5 125 15 1340 69 3 85 12 80.0 200 15 1310 65 1 93 13 92.0 10 15 1420 73 3 80 0 41 14 91.3 02 03 01 01 @0 15 1340 74 4 83 0 40 15 79.5 05 0.5 03 0.2 01 15.0 15 1340 73 3 78 0 40 16 3.0 20.0 3.0 6.0 10 0 40 10.0 15 1420 82.3 58 0 47 17 70.0 30.0 15 1300 71.4 65 0 40 18 70 0 30.0 15 1200 70.3 68 19 88.0 2.0 10.0 15 1400 71.5 74 20 90.0 0.7 10.0 15 170OHP81.7 54 0.42 21 91.6 0.7 6.7 1.0 15 170OHP81.7 54 1 83.5 6.5 0 * 1360 91.4 180 0.56 C 2 83.5 6.5 60 * 1400 K K 3 40* 60 * 15 1100 50.3 78 Notes * outside scope of claims.HP: Sintering done by hot pressing at 100 kg/cm *1#@c/TIC/TaC. **1#/Tlc,TIN Table 1 Captions a. Material Types b. Materials of the Present Invention c. Comparative Materials d. Matrix Material Blending Compositions wt% e. BN Addition Amount vol% f. Sintering Temperature ( C) g. Hardness (HRA) Not sintered 2 h. Deflective Strength (kg/mm2) Not sintered i. Coefficient Of Friction (p) k. Could not be measured.

Table 2

at % d e f g h i j a (HaA) (kg/@@) @ ve Co SIC SI2H4 MgO Al2O@ IN TIS2 T1S2 VaS graphite MoS2 @ 22 93.5 6 5 15 0 1360 74 5 78 0 43 23 93 5 6 5 15 0 1360 74.0 81 24 93.5 6.5 15 0 1360 73.2 45 0 45 25 93.5 6.5 12 3 20 1360 74 3 @3 26 93.5 6.5 9 6 40 1360 74 0 @7 0 43 27 93.5 6.5 6 9 60 1360 73.@ 90 28 92 @ @ 2 9 33 1900HP 7@ 3 38 0.47 29 92 5 3 @ 2 5 33 1600N2 75.9 47 0 43 4 93.5 6.5 15 100* 1360 85.3 124 0.50 5 93.5 6.5 15* 1360 87.7 40.5 6 92 4 1900HP 94 5 58 0.60 7 92 5 3 1600N2 93.4 75 0.58 Note * - outside the scope of the claims Table 2 Captions a. Material Types b. Materials Of The Present Invention c. Comparative Materials d. Matrix Material Blending Compositions wt% e. Self-lubricating Material Addition Amount (vol%) f.Amount Of Graphite In Self-lubricating Material (vol%) g. Sintering Temperature ('C) h. Hardness (HRA) i. Deflective Strength (kg/mm2) j. Coefficient Of Friction tp) Table 3

a d e f g b i j (vt %) vc Ca Sic AlN Al2O3 MgO Y2O3 BN Tis2 graphite 30 93.5 6.5 15 1400 87.7 54.3 0.43 31 93.5 6.5 15 1400 83.1 95.4 0.45 32 93.5 6.5 15 1400 91.3 122.9 0.44 33 93.5 6.5 15 1400 90.0 125.4 0.42 34 93.5 6.5 15 1400 89.6 153.2 0.48 b 35 93.5 6.5 30 1400 90.4 132.1 36 93.5 6.5 50 1400 91.0 112.3 0.49 37 93.5 6.5 15 5 1400 78.4 83.1 0.40 38 93.5 6.5 15 5 1400 80.2 102.4 0.41 39 93.5 6.5 15 5 1400 81.3 138.3 0.44 40 93.5 6.5 15 2 2 2 1400 82.8 51.7 0.39 c 8 93.5 6.5 80** 5** 1400 91.8 35 0.55 Note ** two together outside scope of patent claims.

Table 3 Captions a. Material Types b. Materials Of The Present Invention c. Comparative Material d. First Hard Material Blending Compositiom (wt%) e. Second Hard Material Blending Composition (vol%) f. Self-lubricating Material Addition Amount (vol%) g. Sintering Temperature ('C) h. Hardness (HRA) i. Deflective Strength (kg/mm2) j. Coefficient Of Friction (,-1)

Claims

Claims 1. A self-lubricating hard material characterised in that at least one self-lubricating material comprising BN, or a sulfide of Cr, Mn or a transition metal from column IVa to VIa of the periodic table, or a solid solution or double sulfide of these sulfides is dispersed in a proportion of 0. 1 to 50 vol% in hard material comprising a matrix.
2. A self-lubricating hard material characterized in that a) at least one self-lubricating material comprising BN, or a sulfide of Cr, Mn or a transition metal from column IVa to VIa of the periodic table, or a solid solution or double sulfide of these sulfides, and b) carbon that is preferably graphite are dispersed in a proportion of 0. 1 to 50 vol% in hard material comprising a matrix.
3. A self-lubricating hard material as described in Claim 1 or 2, characterised in that the hard material matrix is 50 to 99. 9% wt% WC and the remainder is a hard metal comprising at least one iron family metal.
4. A self-lubricating hard material as described in Claim 1 or 2, characterised in that the hard material matrix comprises at least one hard material comprising a carbide, nitride or boride of a transition metal from column IVa to VIa in the periodic table or two or more of such hard materials in solid solution or as a compound.
5. A self-lubricating hard material as described in Claim 1 or 2, characterised in that 50 to 99. 9 wt% of the hard material comprises at least one hard material comprising a carbide, nitride or boride of a transition metal from column IVa to VIa in the periodic table or two or more of such hard materials in solid solution or as a compound, the remainder comprising one or more iron family metal.
6. A self-lubricating hard material as described in Claim 1 or 2, characterised in that 50 to 99 wt% of the hard material matrix comprises at least one hard material comprising a carbide, nitride or boride of a transition metal in column IVa to VIa in the periodic table or two or more of such hard materials in solid solution or as a compound and the remainder comprises one or more iron family metal, and a portion or all of the hard material is a compound with a portion of iron family metal and/or one or more types of added self-lubricating material.
7. A self-lubricating hard material as described in Claim 1 or 2, characterised in that the hard material matrix is a ceramic comprising at least one of hard material comprising SiC, Si3N4, A1203, A1N, MgO, ZrO2, CaO, Y203 or a carbide, nitride or boride of a transition metal from column IVa to VIa of the periodic table or a solid solution or compound of two or more of these.
8. A self-lubricating hard material characterised in that there is a first hard material that is either a) at least one hard material comprising a carbide, nitride or boride of a transition metal from column IVa to VIa of the periodic table or a solid solution or compound of two or more of such materials, or b) 50 to 99 wt% of at least one hard material as in (a) above, the remainder comprising one or more iron family metal, there is a second hard material comprising at least one hard material comprising SiC, Si3N4, Awl 03, A1N, MgO, ZrO2, CaO, Y203 and an oxide of a rare earth element or a solid solution or compound of two or more of these second hard materials, and the first hard material is substituted in the second hard material in a proportion of 0. 1 to 80 vol%.
9. A self-lubricating hard material as described in Claim 8, characterised in that at least one self-lubricating hard material comprising BN or carbon that is preferably graphite, or a sulfide of Cr, Mn or a transition metal from columns IVa to VIa in the periodic table or a solid solution or double sulfide of these sulfides are dispersed in the hard material matrix in a proportion of 0. 1 to 50 vol%.
10. A self-lubricating hard material, substantially as herein described with reference to any of examples 1 to 40.